Heating high-temperature apparatus



sept. z5, 192s. 1,685,226

C. L. BURDICK HEATING HIGH TEMPERATURE APPARATUS Filed June 25, 1926 /6/INVENT R BY QM .'l ,wml/)Www M ATTORNEYS Patented Sept. 25, 1928.

UNITED STATES 1,685,226 PATENT OFFICE.

CHARLES LALOR BURDICK, OF NEINl YORK, N. Y., ASSIGNOR T GUGGENHEIMBROTHERS, 0F NEW YORK, N. Y., A. GOPABTNERSHII'.

4fnnnzriivci HIGH-TEMPERATURE APPARATUS.

Application led June 25, 1926.

'.l'his invention relates to high temperature apparatus such as furnacesand more particularly metallurgical furnaces. The invention has for itsobject the `provision of improved electric heating for suchhightemperature apparatus, and more particularly kthe invention aims toprovide improved electri-c heating vfor metallurgical furnaces of themultiple hearth type. Y

Heretofo're, one of the chief difficulties with electric heatingelements for metallurgical furnaces and the like has been theiri-naccessibility so that when replacements were re l qui-red, it hasbeen necessary to interrupt the operations of the furnace. Moreover, the

usual materials of whichheating elements are' made will not withstandthe corrosive action of certain gases and materials introduced orgenerated within the furnace.

The present invention contemplates the provision of an improved electricheating unit for metallurgical furnaces, andv more particularly forcircular furnaces such as the multiple hearth furnaces. In accordancewith the invention the electric heating or resistance element isenclosed within a protective tube and suitably mounted within thefurnace# The arrangement of 'support is such that in case'anyreplacement is required, either the entire tube and element may be takenout and andther complete unit put in its place, or if only thelheatingelement requires renewal, the element may be withdrawn from the tube andanother put in its place. A plurality of these heating units in the samefurfnace may be connected'electrically in series or in parallel, and therenewal, in whole or in lpart, of a single unit can be easily madewithout interfering with the operation of the '40v furnace.

, The heating units of the invention are particularly applicable tomultiple hearth furnaces, sluch as the Wedge or MacDougal furnaces. Inthese furnaces, the hearths are so arranged that. there is noopportunity for repair work within the furnace while operating at hightemperatures and for this. reason electrical heating has not heretoforebeen considered practicable.

The novel features of the invention will be best understood from thefollowingy description taken in conjunction with the ac-' companyingdrawing, in which Fig. 1 is a sectional elevation of a single hearth. orheating chamber in a. multiple Serial No. 118,413.

hearth furnace provided with the improved electrical heating means oftheinvention;

Ifig. 2 is a cross section of the furnace of rgenerally along thesection line lposed shaft 3 extends vthrough appropriate centralopenings in the hearths and is adapted to be rotated by an appropriatesource of power (not shown). i

'.lhe shaft 3 carries radially disposed arms 4 positioned above each ofthe hearths. Flows or serapers 5 are attached to the arms 4. The plows 5are arranged to move the charge on adjacent hearths in opposite dire'ctions towards appropriate discharge openings. such as 6 and 8 in Fig. l.

In accordance with my present invention, a plurality of electric heatingunits 9 are radially disposed in cach heating or working' chamber 7 ofthe furnace, and hence above each of the superposed hearths. Thehea-ting units extend through appropriate openings inthe cylindricalside wall of the furnace 'and are supported within the furnace byhangers or brackets 10. A removable bushing or other appropriate packingmeans 13 seals the space between the outer end of each heating unit andthe furnace wall.

The heating unit com-prises a protective tube or casing 14within'whiclris appropriatcly mounted the electric heating element 16.The heating element is supported within the protecting tube byinsulating discs 15, of porcelain, lava rock, asbestos fiber, or otherappropriate material. The terminals 11-12 f of the heating elementextend beyond the .open end of the tube 14 and are appropriatelyconnected to the source of electric energy. In Fig.l 2 of the drawing,the sin heating elements 1G are electrically connected in series and tothe source of electric energy (not shown).

The heating element 16 is spaced from the interior walls of theenclosing tube 14." The element is so constructed as to generate aprogressively increasing amount of heat from the center towards theperiphery of the heating chamber. In a circular furnace, if the heatingelement throughout the length of the protect-ing tube be of uniformconstruction, more heat Will be generated and dissipated per square footof hearth area near the center of the furnace than at the circumference.In order to obviate this difficulty and to maintain a uniformtemperature over the entire` hearth, the number of coils per foot of theheating element are in proportion to the distance from the center of thefurnace. For example, a heating element supported radially within atwenty-foot diameter furnace would have ten coils or turns of resistanceWire or ribbon per footat the `circumference and five turns per foot ata dist-ance of five feet from the center and three turns at a distanceof three feet from the center. T he actual number of turns or coils willvary with the amount of heat, size of Wire, temperature required, etc.,and the example just given is merely to shovvl that the area to beheated under the element is proportional to the distance from the centerof the furnace and that the variation in the number of turns or coilsWill vary in this same proportion or in an otherwise compensated manner.

The Wire or ribbon swerving as the resistance or heating element 16 isso mounted that no part of itv touches the protecting tube let. Thematerial for the heating elements may be of any of the standard metalsor alloys as,l

for instance, nichrome Wire or ribbon. The protecting tubes are made ofany material that will withstand the temperature and the harmful effectof gases, dust, and other materials present in the heating chambersduring the operation of the furnace. Tubes made of 30% ferro-chrome havebeen found satisfactory for' use in the reduction of certain metallicoxides, the metals from which react or alloy with iron or copper etc.'Ihe tubes may also be made of quart-Z, carborundum, and otherappropriate refractories.

The heating units of the invention are of particular advantage inmultiple hearth furnaces, as Well as in other furnaces in which thehearth is circular. Thus, the Aheating units are conveniently supportedWithin the furnace and may be'conveniently removed, in Whole or in part,when replacements are necessary, Without interfering with the operationof the furnace. Moreover, the heating elements are of such construct-ionand so arranged that the circular hearth is uniformly heated over itsentire area by the heat generated in and dissipated tothe hearth byradiation and by conduction through gases. The

invention permits the use of the multiple hearth furnace in operationsfor which it was heretofore unsuited, as, for example, the reduction ofmetallic oxides, such as tin oxide, either by gaseous reduction or bysolid reducing agent.

I claim:

1. The combination with a high temperature apparatus having a heatingchamber of circular section of electric heating units comprising aplurality of elongated electric heating elements each radially disposedin said chamber and of such construction that the amount of heatgenerated by said element progressively increases from the centertowards the perphery of said heating chamber.

Q. rI`he combination with a multiple hearth furnace having substantiallycircular heating chambers, of a plurality of electric heating unitsradially disposed in each of said chambers, each of said unitscomprising an electric heating element mounted Within a protectivecasing of heat refractory material, the heating element being removablefrom its' protective casing and from the furnace and the heating unitbeing removable as a whole from the furnace Without interrupting theoperation thereof.

3. The combination with a multiple hearth furnace having substantiallycircular heating chambers, of a-plurality of electric heating unitsradially disposed in each of said chambers, each of said unitscomprising an electric heating element mounted Within a protectivecasing of heat-refractory material, the heating element being removablefrom its protective casing and from the heating chamber and the heatingunit being removable as a whole from the heating chamber Withoutinterrupting the operation of the furnace, said heating elements beingof such construction that the amount of heat dissipated therefromprogressively increases from the center towards the periphery of theheating chamber.

4. A heating unit comprising a helical coil of gradually increasingpitch from one end to the other mounted within a casing of heatrefractory material in spaced relation to the walls of said casing.

5. A furnace comprising a series of superposed heating chambers, and aplurality of heating elements mounted within each chamber adjacent thetop thereof and extending from points adjacent the side Walls to thecentraly portion of the chamber.

In testimony whereof I affix my signature'.

oHARLEsLALoR BURDICK.

